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目的:通过建立具有不同牙槽骨高度的上颌第一磨牙三维有限元模型,在压力载荷下,计算分析其牙周膜应力的大小和分布,为正畸治疗提供力学参考。方法:采用CT对上颌第一磨牙进行扫描,建立牙槽骨发生不均衡水平吸收的上颌第一磨牙的三维有限元数字模型,计算加载垂直向的压低力时,牙周膜应力的大小和分布。结果:当牙槽骨从正常高度降低3.5 mm时,加载产生的牙周膜应力增加平缓,高应力集中部位在根分叉处;而牙槽骨降低超过6.0mm,根分叉部分暴露时,牙周膜应力明显增加,应力集中的部位转移至根尖及根1/3处。结论:当牙槽骨高度降低未超过6 mm时(牙槽骨吸收未超过根长的48%),应根据牙槽骨的丧失程度来减小矫治力值;当牙槽骨高度降低6 mm以上时(牙槽骨吸收超过根长48%),磨牙的根分叉完全暴露,则应显著减小矫治力值。
OBJECTIVE: To establish a three-dimensional finite element model of maxillary first molar with different height of alveolar bone and calculate and analyze the size and distribution of stress in periodontal ligament under pressure load to provide mechanical reference for orthodontic treatment. Methods: Three-dimensional finite element model of maxillary first molar with unequal horizontal alveolar bone absorption was established by using CT scan of the first molar. The stress and size distribution of the periodontal ligament . Results: When the alveolar bone was reduced by 3.5 mm from normal height, the stress of periodontal ligament produced by loading increased gently and the high stress concentrated area was at the root bifurcation. When the alveolar bone was reduced by more than 6.0 mm, Periodontal ligament stress increased significantly, stress-concentrated sites transferred to the apical and root 1/3 Department. CONCLUSION: When alveolar bone height does not drop below 6 mm (alveolar bone absorption does not exceed 48% of root length), orthodontic force should be reduced according to the loss of alveolar bone. When alveolar bone height is reduced by 6 mm Or more (alveolar bone absorption more than 48% of the root length), molars root bifurcation completely exposed, you should significantly reduce the orthodontic value.